.\" $OpenBSD: X509_sign.3,v 1.11 2024/03/06 02:34:14 tb Exp $
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.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
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.Dd $Mdocdate: March 6 2024 $
.Dt X509_SIGN 3
.Os
.Sh NAME
.Nm X509_sign ,
.Nm X509_sign_ctx ,
.Nm X509_verify ,
.Nm X509_REQ_sign ,
.Nm X509_REQ_sign_ctx ,
.Nm X509_REQ_verify ,
.Nm X509_CRL_sign ,
.Nm X509_CRL_sign_ctx ,
.Nm X509_CRL_verify
.Nd sign or verify certificate, certificate request, or CRL signature
.Sh SYNOPSIS
.In openssl/x509.h
.Ft int
.Fo X509_sign
.Fa "X509 *x"
.Fa "EVP_PKEY *pkey"
.Fa "const EVP_MD *md"
.Fc
.Ft int
.Fo X509_sign_ctx
.Fa "X509 *x"
.Fa "EVP_MD_CTX *ctx"
.Fc
.Ft int
.Fo X509_verify
.Fa "X509 *a"
.Fa "EVP_PKEY *r"
.Fc
.Ft int
.Fo X509_REQ_sign
.Fa "X509_REQ *x"
.Fa "EVP_PKEY *pkey"
.Fa "const EVP_MD *md"
.Fc
.Ft int
.Fo X509_REQ_sign_ctx
.Fa "X509_REQ *x"
.Fa "EVP_MD_CTX *ctx"
.Fc
.Ft int
.Fo X509_REQ_verify
.Fa "X509_REQ *a"
.Fa "EVP_PKEY *r"
.Fc
.Ft int
.Fo X509_CRL_sign
.Fa "X509_CRL *x"
.Fa "EVP_PKEY *pkey"
.Fa "const EVP_MD *md"
.Fc
.Ft int
.Fo X509_CRL_sign_ctx
.Fa "X509_CRL *x"
.Fa "EVP_MD_CTX *ctx"
.Fc
.Ft int
.Fo X509_CRL_verify
.Fa "X509_CRL *a"
.Fa "EVP_PKEY *r"
.Fc
.Sh DESCRIPTION
.Fn X509_sign
signs the certificate
.Fa x
using the private key
.Fa pkey
and the message digest
.Fa md
and sets the signature in
.Fa x .
.Fn X509_sign_ctx
also signs the certificate
.Fa x
but uses the parameters contained in digest context
.Fa ctx .
.Pp
.Fn X509_verify
verifies the signature of certificate
.Fa x
using the public key
.Fa pkey .
Only the signature is checked: no other checks (such as certificate
chain validity) are performed.
.Pp
.Fn X509_REQ_sign ,
.Fn X509_REQ_sign_ctx ,
.Fn X509_REQ_verify ,
.Fn X509_CRL_sign ,
.Fn X509_CRL_sign_ctx ,
and
.Fn X509_CRL_verify
sign and verify certificate requests and CRLs, respectively.
.Pp
.Fn X509_sign_ctx
is used where the default parameters for the corresponding public key
and digest are not suitable.
It can be used to sign keys using RSA-PSS for example.
.Sh RETURN VALUES
.Fn X509_sign ,
.Fn X509_sign_ctx ,
.Fn X509_REQ_sign ,
.Fn X509_REQ_sign_ctx ,
.Fn X509_CRL_sign ,
and
.Fn X509_CRL_sign_ctx
return the size of the signature in bytes for success or 0 for failure.
.Pp
.Fn X509_verify ,
.Fn X509_REQ_verify ,
and
.Fn X509_CRL_verify
return 1 if the signature is valid or 0 if the signature check fails.
If the signature could not be checked at all because it was invalid or
some other error occurred, then -1 is returned.
.Pp
In some cases of failure, the reason can be determined with
.Xr ERR_get_error 3 .
.Sh SEE ALSO
.Xr d2i_X509 3 ,
.Xr EVP_DigestInit 3 ,
.Xr X509_CRL_get0_by_serial 3 ,
.Xr X509_CRL_new 3 ,
.Xr X509_get_pubkey 3 ,
.Xr X509_get_subject_name 3 ,
.Xr X509_get_version 3 ,
.Xr X509_NAME_add_entry_by_txt 3 ,
.Xr X509_NAME_ENTRY_get_object 3 ,
.Xr X509_NAME_get_index_by_NID 3 ,
.Xr X509_NAME_print_ex 3 ,
.Xr X509_new 3 ,
.Xr X509_REQ_new 3 ,
.Xr X509_verify_cert 3 ,
.Xr X509V3_get_d2i 3
.Sh HISTORY
.Fn X509_verify
appeared in SSLeay 0.4 or earlier.
.Fn X509_sign
and
.Fn X509_REQ_sign
first appeared in SSLeay 0.4.4.
.Fn X509_REQ_verify
and
.Fn X509_CRL_verify
first appeared in SSLeay 0.4.5b.
.Fn X509_CRL_sign
first appeared in SSLeay 0.5.1.
These functions have been available since
.Ox 2.4 .
.Pp
.Fn X509_sign_ctx ,
.Fn X509_REQ_sign_ctx ,
and
.Fn X509_CRL_sign_ctx
first appeared in OpenSSL 1.0.1 and have been available since
.Ox 5.3 .
